1. Field of the Invention
This invention relates to real-time computer thermal management, and more particularly to an apparatus and method for decreasing and increasing central processing unit (CPU) clock time based on the temperature levels associated with operation of a CPU in a portable computer.
2. Description of the Related Art
During the development stages of personal computers, the transportable or portable computer has become very popular. Such portable computer uses a large power supply and really represents a small desktop personal computer. Portable computers are smaller and lighter than a desktop personal computer and allow a user to employ the same software that can be used on a desktop computer.
The first generation “portable” computers only operated from an A/C wall power. As personal computer development continued, battery-powered computers were designed. Furthermore, real portability became possible with the development of new display technology, better disk storage, and lighter components. Unfortunately, the software developed was designed to run on desk top computers without regard to battery-powered portable computers that only had limited amounts of power available for short periods of time. No special considerations were made by the software, operating system (MS-DOS), Basic Input/Output System (BIOS), or the third party application software to conserve power usage for these portable computers.
As more and more highly functional software packages were developed, desktop computer users experienced increased performance from the introductions of higher computational CPUs, increased memory, and faster high performance disk drives. Today, portable computer performance is rapidly approaching that of desktop computers. Pentium and 486 processors have a clock frequency of 90 Mhz+ are not uncommon. Unfortunately, these larger and faster processors consume increasingly higher amounts of energy. One byproduct of energy consumption is heat. Heat becomes a problem when the temperature within the CPU rises to a level sufficient to cause adverse computer performance. Overheating is not a big problem in desktop computers due to the relatively large case and board sizes, large heat sinks and ventilating fans of the desktop computers. Portable computers, on the other hand, have limited case and board sizes, relatively small heat sinks and no ventilating fans. Even if portable computers had the space for ventilating fans, there is insufficient battery power to operate them in an efficient manner. To make matters worse, competitive pressures are dictating a trend toward smaller and more compact portable computers having increasingly larger and faster processors.
Thermal over-heating of CPUs and other related devices is a problem yet to be addressed by portable computer manufacturers. CPUs are designed to operate within specific temperature ranges (varies depending on CPU type, manufacturer, quality, etc). CPU performance and speed degenerates when the limits of the operation temperature ranges are exceeded, especially the upper temperature range. This problem is particularly acute with CPUs manufactured using CMOS technology where temperatures above the upper temperature range result in reduced CPU performance and speed. Existing power saving techniques save power but do not measure and intelligently control CPU and/or related device temperature.